Revert "feat: DEL in place of PGDN among the terminal's extra keys"

This reverts commit cf855fdc23.

internal/server/web/templates/terminal.html

@@ -58,7 +58,7 @@
   <button type="button" data-k="left">←</button>
   <button type="button" data-k="down">↓</button>
   <button type="button" data-k="right">→</button>
-  <button type="button" data-k="del">DEL</button>
+  <button type="button" data-k="pgdn">PGDN</button>
 </div>
 
 <script src="/static/xterm.js"></script>
@@ -202,7 +202,7 @@
   }
   // xterm's modifier parameter: 1 + shift(1) + alt(2) + ctrl(4).
   const CSI = { up: 'A', down: 'B', right: 'C', left: 'D', home: 'H', end: 'F' };
-  const TILDE = { del: 3, pgup: 5 };
+  const TILDE = { pgup: 5, pgdn: 6 };
   function keySeq(k) {
     const m = useMods(), p = 1 + (m.alt ? 2 : 0) + (m.ctrl ? 4 : 0);
     if (CSI[k]) {